Exchange system for telegraphs



(No Model.)

'J. H. ROBERTSON.

EXCHANGE SYSTEM FOR TELEGRAPHS. No. 403,291. Patented May 14, 1889.

N, PETERS. Phola-Lnnngrapher, wmin am a. c,

UNITED STATES PATENT OFFICE.

JAMES H. ROBERTSON, OF RUTHERFORD, NEW JERSEY.

EXCHANGE SYSTEM FOR TELEGRAPHS.

SPECIFICATION forming part of Letters Patent No. 403,291, dated May 14, 1889.

Application filed November 23, 1886, Serial No. 219,581. (No model.)

To all whom it may concern:

Be it known that 1, Lucas H. RoBEErsoN, a citizen of the United States, residing in Rutherford, Bergen county, New Jersey, have invented a new and useful Improvement in Exchange or OentralOffice Systems as Applied to Telegraphs, especially Autographic Telegraphs, of which the following is a specification.

This invention is intended to be used in connection with the autographic telegraphs for which I have heretofore filed several applications for Letters Patent, notably application Serial No. 206,692.

The instruments of such a telegraph are of course adjusted to operate at a certain resistance of the circuit- 6. 6., they are so adjusted that they will operate best at a particular resistance. \Vhen, however, numerous instruments located at various points are connected with a central office, it follows that there will be a great difference in the resistance of the several connecting-conductors, and that in those cases where the resistance of the circuit differs widely from that to which the instruments are adjusted the latter will not work satisfactorily, or perhaps not at all. To adjust in each such case the resistance of the instruments would be impracticable, as it would require experienced operators, the employment of which it is desired to make unnecessary. It is therefore desirable to have some means whereby the combined resistance of any two subscriberss lines that maybe connected with each other maybe made approximately the same. I accomplish this object by the means hereinafter described and claimed. In my application hereinbefore referred to I have shown and described the instruments of subscribers connected and operated by two conductors; but for the sake of clearness I have shown in the accompanying drawing only one conductor. It is, however, possible to operate the instruments by only one connecting-conductor, as described in Gowpers English patent, No.1,242 of 1879, for example. In the drawing herewith, forming part of this specification, is shown a construction embody'ing my invention for accomplishing the object I have in view.

In the drawing I have shown six subscrib= ers lines, 1 2 3 4: 5 (5, of, varying resistance, entering a central. office. Two switches, 7 8, electrically connected with each other, are used for connecting the several subscribers with each other. In the conductor connect ing the switches is placed the battery 9. I have shown two lines of two hundred and one hundred ohms resistance connected with each other, making a combined resistance of three hundred ohms, disregarding resistance of battery. If lines 1 and 5 were connected with each other, the combined resistance would be only twenty-two ohms.

As all the instruments of the several subscribers are adjusted approximately the same, it is obvious that the battery suitable for a circuit of three hundred ohms resistance would be too strong for a circuit of only twenty-two ohms resistance. To remedy this diiiiculty I provide each line with an equalizing-resist ance, which, as shown in the drawing, consists of a pile of carbon disks, 10. This resistance is adjusted for each line and is inserted in the same at the central office. N 0 two subscribers lines out of a thousand are likely to be of the same resistance, and hence I add to each line after it has entered the central office sufficient resistance to make all the lines equal in that respect. I prefer to use piles of carbon disks, each pile provided with an adj usting-screw, 11,whereby the resistance can be increased or decreased, as may be found necessary.

'I do not herein lay claim specifically to means whereby the combined resistance of any two conductors that may be connected with each other is made approximately the same, in combination with a number of conductors terminating in a central office, but refer to my application, Serial No. 212,165, filed August 30, 1886, in which I have made specific claims to specific constructions.

Having thus described my invention, What I claim, and desire to secure by Letters Patent, 1s-

1. In autographic telegraphy, the combina tion, with a number of conductors of different resistances extending from the subscribers instruments to and terminating in a central office, of switchingmeans for electrically connecting any two of said conductors, and equal- 10 for adjusting the resistance thereof, whereby the combined resistance of any two conductors that may be connected With each other is made approximately the same, substantially as described.

In testimony whereof I have hereunto sub 15 scribed my name.

JAMES H. ROBERTSON. Vitnesses:

JNo. E. GAVIN, BENJAMIN MILLER. 

